168 BULLETIN OF THE BUSSEY INSTITUTION. 
there was found an amount equal to 4.31% of the plant dried at 110°, 
or to 30.21% of the crude ashes of the plant. Some rough attempts 
were made to determine the amount of silica proper (as distinguished 
from sand) in the sterile stems ; but the results obtained were not sat- 
isfactory. On treating ashes obtained from different portions of one 
and the same sample of the powdered dry plant with caustic soda, 
there was found, in one trial, only as much silicic acid as would 
amount to 1.42% of the plant dried at 110°, while in another trial 
there was found 2.94%, and in a third, 1.33%. In other words, there 
was found 10.45%, 21.70%, and 9.34%, respectively, of silicic acid 
in the three samples of crude ashes. It was proved, furthermore, by 
special qualitative trials, that the process of analysis employed was 
faulty, inasmuch as more or less silicic acid was dissolved out from 
the ashes by the caustic soda accordingly as the lye was applied in a 
stronger or weaker condition, and as it was made to act upon the ashes 
for a longer or shorter time. The behavior of the ashes in respect to 
caustic soda would seem to show that a considerable proportion of their 
silica is not free and uncombined, but held in chemical combination by 
some one or more of the basic ingredients of the ashes. Compare the 
table at end of this article. Lack of material has prevented me from 
studying this question, and from estimating the true amount of silica 
in the ashes. 
The difference between the amounts of nitrogen found in the sterile 
and in the fertile stems is so noteworthy that, for the sake of verifying 
it, I have had the amount of nitrogen estimated in two other species of 
equisetum that happened to be at my disposal; namely, in the fertile 
stems of Hquisetwm limosum and in the sterile and fertile stems of Zguise- 
tum sylvaticum. 'The specimens now in question were collected by Mr. 
Wright, and were taken from his herbarium for analysis. 
In the specimen of Hquisetum limosum, “ in fruit,’ collected in Dor- 
chester, Mass., June 20, 1876, there was found, in two trials (in the 
plant dried at 110° C.) 1.91% and 2.16% of nitrogen, equal to 12.75% 
of albuminoids. In the fertile stems of Hquwisetum sylvaticum, collected 
May 8, 1876, on low, wet, grassy land at Forest Hills (dried at 110° C.), 
there was found 2.17% of nitrogen, — equal to 13.58% of albuminoids. 
In sterile stems of Hquisetum sylvaticum, taken from the same parcel as 
the fertile stems, there was found, after drying at 110° C., 3.67% of 
nitrogen, — equal to 22.94% of albuminoids. These air-dried speci- 
